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Three Years Later Has Public-Key Cryptography (PKC) became practical yet? The answer might still be NO, but … Recent Studies on using PKC on sensors PKC is feasible for WSN ECC signature verification takes 1.6s on Crossbow motes (Gura et al.)

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Let’s Switch to PKC? Sorry, I forgot to mention one thing: The gap between SKC and PKC is not going to change much unless a breakthrough in PKC occurs. Computation costs RC5 is 200 times faster than ECC Communication costs Signatures: ECC (320 bits), RSA (1024 bits), SHA1 (160 bits)

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New Focuses My observation: We will be able to use PKC, but we will use SKC if that can save energy. We are doing this in traditional networks Example: session keys Research Problem Can we reduce the amount of PKC computations with the help of SKC?

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Public Key Authentication Before a public key is used, it must to authenticated In traditional networks: we use certificates. Verifying certificates is a public key operation Can we do it more efficiently in WSN? A simple way: each node carries the hash of other nodes’ public keys Memory usage is too much (N-1 hash values)

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Comparing Energy cost with RSA / ECC Performance of authenticating public keys using various algorithms

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Conclusion and Future Work Public Key Cryptography (PKC) Will soon be available for sensor networks Usage of PKC should still be minimized We propose an efficient scheme to achieve public key authentication. Future work Optimize other PKC computations